Total cell expansion and percent hind limb volume calculation of cultured cells from a representative experiment. Starting cell numbers before expansion are indicated at the top of each triangle and represent either donor volume fractions (vol.) of 0.86 or 1.0 for HaMDR1 or HaDHFR, respectively. Total cell numbers expanded during each culture period and this expansion is represented by a triangle. The cell numbers before replating on days 3, 6, and 12 are indicated inside the base of each triangle. On days 3 and 6 only a fraction of the cells were replated (arrows) while the rest were discarded. This resulted in a decrease in the fraction donor volume remaining. Thus, on day 12 the fraction donor hind limb volume remaining was very low (bottom of each column) despite the significant increase in cell number relative to day 0. The number of cells injected into individual mice, and the corresponding donor volumes they represent, are shown below in parentheses.